Shaped article and method of producing it



Patented May 5, 1953 SHAFEB `RIICILII AND METHGD 0F PRODUCING IT Arthur. vCressrwell, Stamford, Conn., assigner'.l tov American @yann-mid Company, New YorlsN.- Y., a corporation of Maine NoD'rawing.; Application' September 27', 195.1,

Serial No. 248,671

(Cl. 12S-335.5)

13 Claims. l

The present invention 'relatesto" iilamients, threads, strands :and tapes, hereinafter sometimes referred toas shapes or strands "The inven tion-further relates to suchfsliaped articles' oonsisting 'essentially or regenerated'collagenand to methods otiprodu'cing them..

The invention is: particularly. oonoerned with themanuiaoture: ortsuch: strands from collagen orlcolla'gienous rriaterial.A

The shapes' pro'duc'edhyftlie present .invention are particularly"usefurastsurgical .sutures or' lign tures' and have decided advantage over. thor articles normally produced from` intestinal rnaterial known astoatguhf. The present collagenous shapes'maybe pro duced in unlimited lang lhs, are uniform;` throughout their length: to. size, strength,. toughnesslifand. capacity for indirect or heat sterilization. Any desired degree of :tannage may be given such suturesV or: ligatures. in the usual` variety oi tanning baths.

Collagen isa protein which is. an. ingredient of the hide, skin, `iasoialata-.andirnisoles of vertebrates and occurs; therein aslbrous matter, along with a multitudefof. other substances such as hair,

elastin .and other insolublesiromlwhioli ool'- lagen must Ibe separatedbeforeitoan bei suocessfully used according to: theapresent invention.

Collagen yis. itself insoluti-le.- in water butit may, upon suitable. treatment in water: and,` at' an elevated temperature, be converted to' gelatin. Whilegelatin and collagen are both protein, yet they are dissimilar and are not equivalents. Itis well know that gelatin is soluble in water which 'Ls not true of collagen.

lThrov gliout4 the: present` speeific'ation and claims, Where' the words'collagen` or Collageh nous materia are used, it to oe understoodthat the material thereby designated is to be oompletelyA differentiated from gelatin as thetwomaterials are not at all interchangeable in 'carrying out the purposes of the invention'.

Broaolly speaking, the invention contemplates theextrusion of a collagen solution through a smallorince iollowedhy coagulation of the extruded filament. Such' threads may be made oi any desired sizeor shape and' either ooagulated or coller-ed in such shape or spun, twisted or woven together in multi-filament forni iorlarger threads or'shapes. Such strands and tapes, dueto their manner of manufacture, may be produced in unlimited lengths, the dimensions of which are re.- markably uniform throughout their length.

Such strands may be tanned lay the usual methods employed intlietannage of leather, and sutures prepared' therefrom may' be made in vary- Adesirable in using this source of material thatunlimed hicles'lie chosen. These may be fresh-or green-salted cali slin, kip skin or other' hides which are comparatively lov! inl elastin content. Kip shin is preferred because thel collagen therefrom is of optiinurnl viscosity as compared to that of call-f'sliin. These' are fleshed andi unhairfed down to the clean corium which isv that lamination of the animal hide containing' the greatest proportion of collagen. If green-salted tides' are used, the hides should he soaked heiore this treatment also allowed to remain` in the soaking liquid after cleaning until substantially salt free.

After cutting the ooriuin into strips or small piecesior convenience in' handling, the ooriuin is covered with a dilute solution of an organic acid preferably, though not necessarily; in the pli range of from 2 to Any organic' acid is satisfaotory although from 0.0515@ 0.1.6 N orinie aoid or 0.5 to 1.0 N acetic acid arepreierred. Any other: concentration of otherr organic acids naar,r be' used;

The corium is thus allowed` to' swell for' from sixteen to twenty-'four hours' in the acid. solution at temperatures between' l0 and 30 C'. In, this swelling, the hide lmhioes from oneito three times itsownweiglit of liquid butby maintaining the temperature at this point Ibelow 30 C., gelatin forming conditions are definitely avoided.`

Fol-lowing the swelling, the excess liquid is drained oli and tlieswollen oorium mechanically disintegrated, for example, oy a meat grinder, shredder or other 'form oi sub1-dividing mechanism which Will break down the'collagenfibers to the point where dissolution will he facilitated. In the mechanical disintegration step, heat may be developed dueto friction andA it is, therefore, iin;- portant that the necessary steps bev taken to maintain the material during this operation; at temperatures below 30o C.

At this stage andii the mechanical disintegration haslheen line enough, practically' all of` the collagen will have gone into solution.y Where this collagen solution is highly concentrated, it will gel at 35 C. or. below. Therefore, to separate the dissolved. collagen from the insolubles,l it may loe desirable` tol warm it slightly until fluidity has been reached. Thisk will. certainly `be, at a. tem.- perarture no higher than C.,` While warming to this temperature, if mechanical agitation. is carried on, any last traoesofundissolved collagen will dissolve and the Wholeniay then be centri'- fuged and ltered to remove fibers, elastin, hair fragments and other insoluble matter. The filtrate will be a clear heavily concentrated solution of collagen.

While the preferred source of collagen is the corium as this involves handling a material of maximum collagen content with minimum insolubles, yet as a matter of fact, due to the distribution of collagen throughout the animal hide, it may be desirable to disintegrate vthe entire hide followed by collagen solution in dilute organic acid and the separation of the insolubles. Such a process while varying inthe last step in the removal of an excessive amount of insolubles, does extract substantially all the collagen available.

The concentration of the collagen in its solution may be adjusted to a desired content appropriate for spinning by the addition of a further amount of the dilute organic acid solution such as that used for swelling and solution. It is pre- 'ferred that the spinning solution contain from 5 to collagen although solutions of lower or higher collagen concentration may be used.

Before spinning, it is desirable to deaerate in order that there may be no thread interruption due to the passage of air bubbles through the jet orice. Therefore, by maintaining the collagen solution at a temperature slightly above that at which it will gel and applying a vacuum or partial Vacuum, the air contained in the solution may be removed. The warm solution may then be pumped by any suitable means to a spinnerette, that used in the rayon industry for this purpose being eminently satisfactory, and then immersed in a coagulating bath.

This type of extrusion, that is, from' solution, is to be distinguished from the method such as 'extrusion of a pulp of swollen collagen, not in solution and skin containing insolubles. Such a method is distinctly disadvantageous as large sized orices are required and the filaments resulting therefrom are non-uniform as to size, strength and the like due to the non-uniformity of collagen content.

Strong salt solutions have been found satisfactory as coagulating baths, su-ch as a 35% to saturated solution of ammonium sulfate with sufiicient free ammonia to maintain a pH of 7.8, which is an isoelectric point of collagen. The free ammonia is useful for the purpose of neutralizing the organic acid introduced by the spinning solution, Another satisfactory bath is one containing by weight of magnesium sulfate, buffered with triethanolarnine to a pH of 7.8. Regardless of the particular coagulant used, it

is highly desirable that the bath be maintained at from 20 to 30 C.

It has been found that collagen solutions of the concentrations above mentioned may be extruded into a coagulating bath as above described from spinnerettes with orifices of from' 50 microns to 1 mm., but preferably from 75 to 250 microns in diameter. The lament or thread may be passed over a plurality of revolving wheels commonly called godets which have in-creasing peripheral speeds so that a stretch is imparted to the lament or thread. Following this, the filament or thread may be taken up by a revolving spool which may or may not impart a further stretch. Satisfactory filaments have been spun as above from a spinnerette with orices measuring 110 microns in diameter to a iinished filament at the rate of 80 meters a minute. At this rate, the jetted material remains in contact with the coagulating bath for less than one second.

Adhering coagulants may then be washed from the lament or thread by passing the same in contact with water at a temperature below that at which softening will occur such as less than 20 C. The washed lament or thread may then be dried in air heated to from room temperature to 60 C. However, the lower the temperature the less damage may occur to the treated material.

Where a multi-filament strand is desired, a multi-hole spinnerette may be used. When spinning onto spools, the resulting strand is washed, dried and then twisted. It is also possible to twist the strand while spinning by collecting the strand in a centrifugal pot as commonly practiced in Viscose rayon pot spinning.

Single or multi-lament strands may be tanned in baths commonly used ior the tannage of surgical sutures from gut to determine the degree of body absorption which would be characteristic of the nished article.

It has been noted that when the wet iilaments from' the -coagulating bath are twisted together to form a strand and permitted to remain in contact with each other without drying, a coalescence or cohesive action occurs which tends to make a unitary strand out of the laments. Thus, if a large single coherent strand is desired to be made from a number of smaller filaments, it is only necessary to spin the desired number of lilaments with the coagulating bath, arrange them in contact with each other and keep them wet until coalescence occurs. Thus any size or shape of strand er tape may be secured.

By using suitable godets, any desirable degree of stretch may be imparted to the spin nlaments. Oi course, the degree of stretch will determine in large measure the degree of fiber orientation in the nished lament, thread or strand. Reasonably satisfactory orientation has been obtained through stretching a lament to an extent equal to 700% by using a combination of godets having increasing peripheral speeds.

This application is a continuation-in-part of copending application Serial No. 527,339, iiled March 20, 1944, now abandoned.

While the invention has been described with particular reference to specic embodiments, it is to be -understood that it is not to be limited thereto but is to be construed broadly and restricted solely by the scope of the appended claims.

I claim:

1. A shaped article consisting essentially of regenerated collagen free from nbers and any other material insoluble in a dilute aqueous solution of an organic acid.

2. A shaped article consisting essentially of regenerated collagen free from bers and any other material insoluble in a dilute aqueous solzuttioqn of an organic acid in the range of pH 3. A shaped article consisting essentially of coalesced filaments of regenerated collagen free from bers and any other material insoluble in a dilute aqueous solution of an organic acid.

fi. A method of making a regenerated collagenous shape which includes the steps of dissolving collagen from collagenous material in a dilute aqueous solution of an organic acid removing all insolubles including bers from said solution While maintaining the temperature of said solution above its gelling point but below a temperature at which substantial conversion to gelatin occurs, extruding the thus heated solution into a -coagulating bath and removing the coagulated shape therefrom.

5. The method of claim 4 in which the concentration of collagen in the extrusion solution is from 5% to 15%.

6. A method of matting a regenerated collagenous shape which includes dissolving collagen from collagenous material by soaking and swelling said collagenous material in an aqueous solution of an organic acid at a pH of substantially 2-4, mechanically disintegrating said swollen coalageous material in said dilute aqueous solution of an organic acid, removing all insolubles including fibers from said solution while maintaining the temperature of said solution above its gelling point but below a temperature at which substantial conversion to gelatin occurs, extruding the thus heated solution into a, coagulating bath and removing the ooagulated shape therefrom.

7. The method of claim 6 in which the coagulated shape is stretched after extrusion to 700%.

8. The method of claim 6 in which the collagenous material is animal corium.

9. The method of claim 6 in which the collagenous material is corium from kip skin.

10. A method of making a regenerated collagenous strand Which includes dissolving collagen from collagenous material by soaking and swelling said collagenous material in `an aqueous solution of an organic acid 'at `a pli of substan" tially 2-4, mechanically disintegrating said swollen collagenous material 'in said aqueous solution of an organic acid, removing all insolubles including iibers from said solution While maintaining the temperature of said solution in the range oi substantially 35-59 C., eXtruding the thus heated solution into a coagulating bath and removing the coagulated strand therefrom.

11. The method of claim 10 in which the collagen solution is deaerated before spinning.

12. A method of making a collagen multi-lament suture strand which comprises extruding a :liber-free, Iaqueous organic acid solution Vof collagen maintained at a temperature above its gelling point but below a tempera-ture at which substantial conversion to gelatin occurs, through a multi-holed spinnerette into a coagulating bath, removing the thus spun filaments from the bath and Washing and drying said laments While held apart from each other and then twisting the filaments into a strand..

13. The method of claim 12 in Which the collagen solution is dissolved in an aqueous organic acid solution having a pli of substantially 2-4, the concentration of collagen being 5-15% `and the `solution being deaerated before spinning.

ARTHUR CRESSWELL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,949,111 Randall Feb. 27, 1934 2,039,262 Schulte Apr. 28, 1936 2,126,344 Pierson Aug. 9, 1938 2,120,851 Becker et al June 14, 1938 2,475,697 CressWell July 12, 1949 2,476,293 Hall et al July 19, 1949 2,485,958 Cresswell Oct. 25, 1949 2,517,694 Merion et al Aug. 8, 1950 OTHER REFERENCES Publication: Kolloid-Zeitschrift Band 101,

Heft 2 (1942), Dn. 149-156. Article by Von A. V. Buzagh Uber die Bedingungen der Entstehung kunsthicher Kollagenfasern. 

1. A SHAPED ARTICLE CONSISTING ESSENTIALLY OF REGENERATED COLLAGEN FREE FROM FIBERS AND ANY OTHER MATERIAL INSOLUBLE IN A DILUTE AQUEOUS SOLUTION OF AN ORGANIC ACID. 